The present invention concerns a process for drying wet organoborane compounds.
Certain organoborane compounds (boron hydride compounds in which hydrogen is substituted with organic moieties) are known to be useful as promoters in hydrocyanation reactions. A commercially important hydrocyanation reaction that utilizes these promoters is the conversion of pentenenitrile compounds to adiponitrile. For example, U.S. Pat. No. 3,496,218 describes a process for hydrocyanation of non-conjugated ethylenically unsaturated organic compounds, such as 3-pentenenitrile, in the presence of a nickel/triarylphosphite catalyst and a triorganoborane compound promoter, such as triphenylborane, to produce adiponitrile. Adiponitrile is an intermediate in the production of hexamethylene diamine, a nylon-6,6 component. Adiponitrile is also an intermediate in the production of caprolactam and nylon-6.
Organoborane compounds are easily hydrolyzed. For example, triphenylborane can be hydrolyzed to diphenylborinic and phenylboronic acids in the presence of water. Even at low temperatures (for example, below 10xc2x0 C.), triphenylborane will slowly hydrolyze to diphenylborinic and phenylboronic acids with trace amounts (e.g. 10 ppm) of water present. At elevated temperatures, the hydrolysis rate significantly increases. It is important to dry organoborane compounds which are used as promoters in hydrocyanation reactions, because many hydrocyanation reactions occur at elevated temperatures. Current drying methods include exposure of organoborane compounds to hot nitrogen and molecular sieves. Use of hot nitrogen leads to degradation of some organoborane to undersirable organoborinic and boronic acids. As a result, there is a need in the art for an improved method of drying organoborane compounds that minimizes the production of such undesirable degradation products.